Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L23/00—Details of semiconductor or other solid state devices
  • H01L23/16—Fillings or auxiliary members in containers or encapsulations, e.g. centering rings
  • H01L23/18—Fillings characterised by the material, its physical or chemical properties, or its arrangement within the complete device
  • H01L23/26—Fillings characterised by the material, its physical or chemical properties, or its arrangement within the complete device including materials for absorbing or reacting with moisture or other undesired substances, e.g. getters
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/0001—Technical content checked by a classifier
  • H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
  • H01L2924/095—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00 with a principal constituent of the material being a combination of two or more materials provided in the groups H01L2924/013 - H01L2924/0715
  • H01L2924/097—Glass-ceramics, e.g. devitrified glass
  • H01L2924/09701—Low temperature co-fired ceramic [LTCC]

Definitions

• the present invention relates to a method of reducing the water moisture content in a hermetic package containing a semiconductor device to minimize the possibility of damage to the semiconductor device which may be caused by the presence of water in the package.
• Hermetic packages for semiconductor devices are typically ceramic packages sealed with caps or lids using glass or metal seals. Hermetic sealing is employed to prevent entry into the package of undesirable chemicals which could damage the semiconductor device contained therein. However, the presence of moisture, even in very small or trace amounts, within the hermetic package can also damage the semiconductor device. To avoid any damage to the semiconductor device from moisture contained witi in the package after hermetic sealing, it is necessary to have the moisture content less than 5,000 ppm, otherwise moisture induced corrosion failure of the semiconductor device may result.
• One of the sources of moisture in the package can be the inorganic adhesive used to attach the semiconductor device to a substrate.
• inorganic adhesive such as silver filled glass paste have been used. These adhesives do not release moisture upon heating for curing.
• common die attach adhesive containing polymers, epoxy, polyimide, etc. give off moisture upon heating for curing and therefore cannot be used where low moisture conditions within the hermetic package are required.
• the present invention provides a method of reducing the water moisture content in a hermetic package containing a semiconductor device to prevent damage to the semiconductor.
• a method of reducing the water moisture content which comprises incorporating within the package a small but effective amount of a cyanate ester.
• the cyanate ester is reacted with water moisture to produce an intermediate imidocarbonic acid which becomes moleculariy rearranged upon formation into a stable carbamate molecular structure.
• the carbamate Upon exposure of the molecular carbamate structure to an elevated temperature such as would be used to cure the die attach adhesive securing the semiconductor device to the substrate, the carbamate further reacts with water to produce carbon dioxide.
• the presence of carbon dioxide within the hermetic package is not deleterious or damaging to the semiconductor device and corrosion of the device, as may be induced by the presence of water moisture within the package, is thereby avoided.
• Figure 1 is a description of the chemical reactions which the cyanate ester undergo to reduce the moisture content within a hermetic package
• Figure 2 is a graph showing the effects of aging at 150 °C comparing the amount of moisture and carbon dioxide which is released.
• cyanate ester undergoes the chemical reactions described in Figure 1. As can be seen, the cyanate ester reacts with the water moisture to produce an imidocarbonic acid as an intermediate which quickly rearranges upon formation into a stable carbamate.
• the carbamate upon exposure to an elevated temperature of at least 100°C yields carbon dioxide which is not injurious to semiconductor device in the package.
• the cyanate ester may be incorporated within the package in any suitable manner.
• One manner of incorporating cyanate ester in the package is to incorporate it in a die attach adhesive. Examples of suitable die attach adhesive compositions in which cyanate ester has been incorporated appear below in Table I.
• the moisture content in a hermetic pack in which the cyanate ester has been incorporated has been found to be extremely low. In fact, the moisture content is even lower than that of a blank cavity or of package which does not contain any adhesive or other source of moisture.
• the data shown in Table II compares the moisture content for polyimide, epoxy die attach materials, a blank hermetic package, and a package in which cyanate ester has been incorporated.
• the moisture content in a package employing epoxy resin but which does not include cyanate ester within it is 57,500 ppm as compared to less than 100 ppm moisture in a comparably sized ceramic package in which cyanate ester has been incorporated.
• Two common methods of sealing hermetic packages containing semiconductor devices are to braise a lid, such as a gold plated "Kovar" lid, onto the package with a suitable gold alloy such as an Au-Sn alloy.
• Another method is glass sealing.
• glass sealing a glass is used to form a sandwiched seal between a ceramic lid and a ceramic substrate.
• glass sealing is more popular because of its lower cost.
• current techniques of glass sealing require sealing temperatures well above 400 °C and are therefore not suitable for many applications because such elevated temperatures may damage some semiconductor devices.
• a cyanate ester into the standard ceramic hermetic package is to apply a small amount of cyanate ester to the backside of the lid, such as either a "Kovar" lid or ceramic lid.
• a formulation may comprise a cyanate ester compound.
• the formulation may also include fillers, alumina and/or silicon carbide.
• the package and lid is then sealed at an elevated temperature, e.g., 275°C to 400°C.
• a small amount of alkylphenol and/or a metal curing catalyst may be added to the cyanate ester to increase adhesiveness.

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• Physics & Mathematics (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)
• Structures Or Materials For Encapsulating Or Coating Semiconductor Devices Or Solid State Devices (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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Publications (1)

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Cited By (1)

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Citations (6)

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• 1992
  • 1992-02-28 US US07843735 patent/US5195299B1/en not_active Expired - Lifetime
• 1993
  • 1993-02-25 WO PCT/US1993/001623 patent/WO1993016921A1/en active Application Filing
  • 1993-02-25 AU AU37762/93A patent/AU3776293A/en not_active Abandoned
  • 1993-02-26 MX MX9301072A patent/MX9301072A/es unknown
  • 1993-03-02 TW TW082101538A patent/TW239898B/zh active

Patent Citations (6)

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